R&D Report 1955-04 : Colour television: The effect of picture-tube-characteristic non-linearity on the brightness of a monochrome compatible picture. D. Maurice It is shown that in a colour television system, using the standard N.T.S.C. method of gamma correction, the deterioration in panchromaticity of the monochrome compatible picture can be reduced by the presence of the dot pattern due to the chrominance sub-carrier. A "notch" or sub-carrier elimination filter is thus undesirable in monochrome receivers. In the case of a true constant luminance type of N.T.S.C. system the presence of the chrominace signal on the monchrome screen is deleterious although the deterioration caused by it is by no means as great as the improvement to be obtained from its presence in the case of the standard N.T.S.C. system. A black-to-blue transition is taken to illustrate these effects and one or two others of a transient nature.